double GetAverageLineInfo(
Size availableSize,
VirtualizingLayoutContext context,
FlowLayoutState flowState,
double avgCountInLine)
{
// default to 1 item per line with 0 size
double avgLineSize = 0;
avgCountInLine = 1;
MUX_ASSERT(context.ItemCount > 0);
if (flowState.TotalLinesMeasured == 0)
{
var tmpElement = context.GetOrCreateElementAt(0, ElementRealizationOptions.ForceCreate | ElementRealizationOptions.SuppressAutoRecycle);
var desiredSize = flowState.FlowAlgorithm.MeasureElement(tmpElement, 0, availableSize, context);
context.RecycleElement(tmpElement);
int estimatedCountInLine = Math.Max(1, (int)(Minor(availableSize) / Minor(desiredSize)));
flowState.OnLineArranged(0, estimatedCountInLine, Major(desiredSize), context);
flowState.SpecialElementDesiredSize = desiredSize;
}
avgCountInLine = Math.Max(1.0, flowState.TotalItemsPerLine / flowState.TotalLinesMeasured);
avgLineSize = Math.Round(flowState.TotalLineSize / flowState.TotalLinesMeasured);
return(_uno_lastKnownAverageLineSize = avgLineSize);
}
protected internal override void InitializeForContextCore(VirtualizingLayoutContext context)
{
var state = context.LayoutState;
FlowLayoutState flowState = default;
if (state != null)
{
flowState = GetAsFlowState(state);
}
if (flowState == null)
{
if (state != null)
{
throw new InvalidOperationException("LayoutState must derive from FlowLayoutState.");
}
// Custom deriving layouts could potentially be stateful.
// If that is the case, we will just create the base state required by FlowLayout ourselves.
flowState = new FlowLayoutState();
}
flowState.InitializeForContext(context, this);
}
